JP2008261275A - Exhaust emission control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a fear of insufficient purification of an exhaust gas due to drop of the temperature of the exhaust gas, in an exhaust emission control device 1 purifying an exhaust gas of an engine by a reducer. <P>SOLUTION: This exhaust emission control device 1 is provided with a valve device 15 operating the opening of a passage 10, and an exhaust gas temperature sensor 16 detecting the temperature of the exhaust gas. An ECU 16 controls the valve device 15 in accordance with the value detected from the exhaust gas temperature sensor 16. Thereby, a heat removing amount from the injected reducing agent can be reduced by reducing the supply amount of the reducing agent as a cooling medium. Thereby, even when the temperature of the exhaust gas is dropped and the heat quantity of the exhaust gas is reduced, heat of vaporization of the reducer can be secured by reducing the supply amount of the reducer as a coolant and restraining heat removed from the injected reducer itself. As a result, purification of the exhaust gas can be surely executed by preventing vaporization of the reducer and NH<SB>3</SB>generation by decomposition of urea from becoming insufficient even when the temperature of the exhaust gas is dropped. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an exhaust gas purification apparatus that purifies exhaust gas of an engine with a reducing agent.

Conventionally, exhaust gas purification apparatuses that reduce and purify nitrogen oxide (NO _x ) contained in engine exhaust gas with a reducing agent are known. This reducing agent is, for example, urea water, and ammonia (NH ₃ ) generated by decomposition of urea reacts with NO _x by a catalyst to generate harmless nitrogen (N ₂ ) and water (H ₂ O). Thus, NO _x is purified.

  By the way, in this exhaust gas purification device, there is an exhaust valve in which an addition valve for injecting a reducing agent is directly attached to the exhaust pipe. In such an exhaust gas purification device, the tip of the addition valve including the injection hole is the exhaust pipe. Protrusively inside. The reducing agent is directly injected into the exhaust pipe through which the exhaust gas passes, and after being mixed with the exhaust gas, is guided to the catalyst.

  For this reason, the tip of the addition valve is heated by being exposed to high-temperature exhaust gas, and further, heat is transferred from the tube wall that becomes high temperature by receiving heat from the exhaust gas, and the temperature is increased. Therefore, a jacket through which the refrigerant flows is provided in the body of the addition valve, and the addition valve is cooled by circulating the refrigerant in the jacket (see, for example, Patent Document 1).

By the way, the decomposition reaction from urea to NH ₃ is not promoted unless urea water as a reducing agent is vaporized. For this reason, the exhaust gas purification apparatus employs a configuration in which the heat of the exhaust gas is used as the vaporization heat of the urea water, and the urea water heating operation contrary to the cooling operation of the addition valve is not performed separately.

However, the temperature of the exhaust gas varies depending on the operating state of the engine. For this reason, when the temperature of the exhaust gas is low and the exhaust gas cannot give sufficient heat of vaporization to the urea water, the urea water is insufficiently vaporized. As a result, the amount of NH ₃ produced is reduced and NO _x is reduced. There is a risk that purification will be insufficient.
Japanese translation of PCT publication No. 2002-503783

  The present invention has been made in order to solve the above-described problems, and an object of the present invention is to exhaust gas purification apparatus for purifying engine exhaust gas with a reducing agent, and exhaust gas purification becomes insufficient due to a decrease in exhaust gas temperature. It is to reduce the fear.

[Means of Claim 1]
The exhaust gas purifying apparatus according to claim 1 is attached to an exhaust pipe through which exhaust gas from an engine passes, and an addition valve that injects a reducing agent stored in a predetermined supply source into the exhaust pipe and is cooled by a refrigerant; Refrigerant supply means for supplying refrigerant to the addition valve, cooling capacity variable means for varying the amount of refrigerant supplied to the addition valve, temperature detection means for detecting the temperature of the addition valve, and detection obtained from the temperature detection means And a control means for controlling the cooling capacity variable means according to the value.

  Thereby, the exhaust gas purification apparatus can increase or decrease the amount of refrigerant supplied to the addition valve in accordance with the temperature of the addition valve. Since the temperature of the addition valve fluctuates according to the temperature of the exhaust gas, the exhaust gas purification device increases or decreases the amount of refrigerant supplied to the addition valve according to the temperature of the addition valve, resulting in the amount of heat of the exhaust gas. Accordingly, the amount of refrigerant supplied to the addition valve can be increased or decreased.

  Here, since the refrigerant also removes heat from the reducing agent flowing inside the addition valve by cooling the addition valve, if the amount of refrigerant supplied to the addition valve decreases, the amount of heat removed from the reducing agent by the refrigerant decreases. To do. For this reason, even if the exhaust gas temperature decreases and the amount of heat of the exhaust gas decreases, the heat of vaporization of urea water can be ensured by reducing the amount of refrigerant supplied to the addition valve and suppressing the heat removal from the reducing agent itself. it can.

As described above, in the exhaust gas purification device that purifies the exhaust gas of the engine with the reducing agent, it is possible to reduce the possibility that the exhaust gas purification becomes insufficient even if the exhaust gas temperature is lowered.
Note that the NO _x purification reaction by NH ₃ in the catalyst is also not promoted as the temperature decreases. That is, the lower the exhaust gas temperature after injection of the reducing agent, the lower the NO _x purification rate. Therefore, the exhaust gas purification device according to claim 1 is also effective in terms of promoting this purification reaction.

[Means of claim 2]
According to the exhaust gas purification apparatus of the second aspect, the refrigerant is a reducing agent, and the refrigerant supply means is a supply pump that sucks the reducing agent from a supply source and pumps it toward the addition valve. Further, the exhaust gas purification apparatus includes a reducing agent flow passage provided to return the reducing agent pumped by the supply pump to the addition valve as a refrigerant and to return the reducing agent that has cooled the addition valve to the supply source, The cooling capacity variable means is a valve device that is arranged at any position of the reducing agent flow passage and changes the flow rate of the reducing agent in the reducing agent flow passage.

  Thereby, the heat exchange part between an addition valve and a reducing agent can be included in a reducing agent flow path, and a reducing agent can be circulated between a heat exchange part and a supply source. For this reason, the addition valve can be efficiently cooled.

[Means of claim 3]
According to a third aspect of the present invention, the exhaust gas purifying apparatus includes an injection flow path that branches from the reducing agent flow passage and through which the reducing agent injected into the exhaust pipe flows.

[Means of claim 4]
According to the exhaust gas purification apparatus of the fourth aspect, the temperature detection means is exhaust gas temperature detection means for detecting the temperature of the exhaust gas passing through the exhaust pipe.
Thereby, the exhaust gas purification apparatus can directly grasp the temperature of the exhaust gas corresponding to the heat quantity of the exhaust gas. For this reason, the control for ensuring the heat of vaporization of the urea water can be performed with higher accuracy.

[Means of claim 5]
According to the exhaust gas purifying apparatus of the fifth aspect, the refrigerant is engine cooling water, and the refrigerant supply means is a water pump that discharges the cooling water toward the engine. The cooling capacity varying means is a valve device that varies the flow rate of cooling water from the water pump toward the addition valve.
This means shows one form of the exhaust gas purifying apparatus using engine cooling water as the refrigerant.

  The exhaust gas purification apparatus of the best mode 1 is mounted on an exhaust pipe through which exhaust gas of an engine passes, and an addition valve that injects a reducing agent stored in a predetermined supply source into the exhaust pipe and is cooled by the refrigerant, and a refrigerant Is supplied to the addition valve, a cooling capacity variable means for changing the amount of refrigerant supplied to the addition valve, a temperature detection means for detecting the temperature of the addition valve, and a detection value obtained from the temperature detection means And a control means for controlling the cooling capacity variable means according to the above.

  According to this exhaust gas purifying apparatus, the refrigerant is a reducing agent, and the refrigerant supply means is a supply pump that sucks the reducing agent from a supply source and pumps it toward the addition valve. Further, the exhaust gas purification apparatus includes a reducing agent flow passage provided to return the reducing agent pumped by the supply pump to the addition valve as a refrigerant and to return the reducing agent that has cooled the addition valve to the supply source, The cooling capacity variable means is a valve device that is arranged at any position of the reducing agent flow passage and changes the flow rate of the reducing agent in the reducing agent flow passage.

Further, the exhaust gas purification apparatus includes an injection flow path that branches from the reducing agent flow passage and through which the reducing agent injected into the exhaust pipe flows.
The temperature detection means is exhaust gas temperature detection means for detecting the temperature of the exhaust gas passing through the exhaust pipe.

  According to the exhaust gas purification apparatus of the best mode 2, the refrigerant is engine cooling water, and the refrigerant supply means is a water pump that discharges cooling water toward the engine. The cooling capacity varying means is a valve device that varies the flow rate of cooling water from the water pump toward the addition valve.

[Configuration of Example 1]
The structure of the exhaust gas purification apparatus 1 of Example 1 is demonstrated using FIG.
The exhaust gas purification device 1 supplies a reducing agent to the exhaust gas of the engine, and reduces and purifies nitrogen oxides (NO _x ) contained in the exhaust gas. The reducing agent is, for example, urea water, and ammonia (NH ₃ ) generated by decomposition of urea reacts with NO _x by a catalyst to generate harmless nitrogen (N ₂ ) and water (H ₂ O). Thus, NO _x is purified.

  The exhaust gas purification apparatus 1 includes an addition valve 3 that injects a reducing agent into an exhaust pipe 2 through which exhaust gas passes, a supply pump 5 that sucks the reducing agent from a predetermined tank 4 and discharges the reducing agent toward the addition valve 3, And an electronic control unit (ECU) 6 that controls the operation of the valve 3 and the supply pump 5.

  The addition valve 3 is directly attached to the exhaust pipe 2, and a tip portion 9 including an injection hole (not shown) projects into the exhaust pipe 2. And the front-end | tip part 9 is provided with the jacket (not shown) in which the reducing agent as a refrigerant | coolant flows, and the addition valve 3 is cooled by supplying a reducing agent to a jacket. That is, the tip portion 9 is heated by being exposed to high-temperature exhaust gas during engine operation, and further, heat is transferred from the tube wall that is heated by heat received from the exhaust gas.

  Therefore, a jacket is provided at the tip 9 and a reducing agent is circulated through the jacket as a refrigerant to remove heat directly transmitted from the exhaust gas and heat transmitted through the tube wall. The reducing agent as the refrigerant is guided from the supply pump 5 to the jacket through the flow path 10. Then, the reducing agent flowing out from the jacket is returned to the tank 4 through the flow path 11. That is, the flow paths 10 and 11 are provided so that the reducing agent pumped by the supply pump 5 is guided to the addition valve 3 as a refrigerant, and the reducing agent that has cooled the addition valve 3 is returned to the tank 4. Functions as a road.

Further, the reducing agent is guided to the internal flow path (not shown) of the addition valve 3 that leads to the injection hole by the flow path 12 branched from the flow path 10 and is injected into the exhaust pipe 2. That is, the internal flow path of the addition valve 3 communicating with the flow path 12 and the injection hole functions as an injection flow path through which the reducing agent injected into the exhaust pipe 2 flows. The injected reducing agent is mixed with the exhaust gas and vaporized by the heat of the exhaust gas, and the vaporized urea is further decomposed into NH ₃ . Then, the exhaust gas containing NH ₃ is guided to the catalyst, and NO _x is purified by NH ₃ .

  The supply pump 5 functions as a refrigerant supply unit that supplies the reducing agent to be injected to the addition valve 3 and supplies the reducing agent as a refrigerant to the jacket of the addition valve 3 through the flow path 10. The supply pump 5 includes, for example, a rotor having a permanent magnet and a stator around which a coil is wound, and generates a torque by the interaction between a magnetic field generated by the permanent magnet and a current supplied to the coil. (Not shown) is an actuator. Then, the ECU 6 controls the energization of the coil, thereby changing the rotation speed of the brushless motor and operating the discharge amount of the reducing agent.

  The ECU 6 is a well-known microcomputer including a CPU, a ROM, a RAM, and other storage devices, an input device, an output device, and the like that perform a control function and an arithmetic function. The actuators of various devices such as the pump 5 are commanded to control the drive of the devices.

  Further, the exhaust gas purification apparatus 1 includes a valve device 15 that changes the flow rate of the reducing agent in the flow paths 10 and 11 by manipulating the opening degree of the flow path 10 downstream of the branch point with the flow path 12, and an exhaust pipe 2 and an exhaust gas temperature sensor 16 for detecting the temperature of the exhaust gas passing through 2. The valve device 15 functions as a cooling capacity varying unit that varies the supply amount of the reducing agent as the refrigerant to the addition valve 3. Further, the exhaust gas temperature sensor 16 functions as temperature detection means for detecting the temperature of the addition valve 3 by detecting the temperature of the exhaust gas. The ECU 6 functions as a control unit that controls the valve device 15 as a cooling capacity variable unit in accordance with a detection value obtained from the exhaust gas temperature sensor 16.

  Here, the valve device 15 is, for example, a well-known solenoid electromagnetic valve capable of operating the opening degree of the flow path 10 in accordance with an energization amount to a solenoid coil (not shown). Then, the ECU 6 controls the opening degree of the flow path 10 by varying the energization amount to the solenoid coil of the valve device 15 according to the detection value obtained from the exhaust gas temperature sensor 16.

[Effect of Example 1]
The exhaust gas purification apparatus 1 according to the first embodiment includes a valve device 15 that varies the flow rate of a reducing agent as a refrigerant by operating the opening degree of the flow path 10 downstream from the branch point with the flow path 12, and the exhaust pipe 2. The exhaust gas temperature sensor 16 for detecting the temperature of the exhaust gas passing through the ECU 6 controls the valve device 15 according to the detection value obtained from the exhaust gas temperature sensor 16.
Thereby, the exhaust gas purification apparatus 1 can increase / decrease the supply amount of the reducing agent as the refrigerant according to the heat quantity of the exhaust gas. Here, the reducing agent as the refrigerant also removes heat from the reducing agent injected through the addition valve 3 by cooling the addition valve 3. For this reason, the amount of heat removal from the injected reducing agent can be reduced by reducing the supply amount of the reducing agent as the refrigerant. As a result, even if the exhaust gas temperature decreases and the amount of heat of the exhaust gas decreases, the amount of reducing agent supplied as a refrigerant is reduced, and the heat of vaporization of the reducing agent is reduced by suppressing heat removal from the injected reducing agent itself. Can be secured.

As described above, in the exhaust gas purifying apparatus 1, even if the exhaust gas temperature is lowered, it is possible to reliably purify the exhaust gas by avoiding insufficient generation of NH ₃ due to vaporization of the reducing agent and decomposition of urea. .
Note that the NO _x purification reaction by NH ₃ in the catalyst is also not promoted as the temperature decreases. That is, since the purification rate of about exhaust gas temperature after the reducing agent injection is low NO _x is reduced, in terms of the purification reaction promotion, the above construction of an exhaust gas purification device 1 is effective.

The reducing agent flow passage is configured to include a heat exchange portion (that is, the above-described jacket) between the addition valve 3 and the reducing agent as the refrigerant.
Thereby, since a reducing agent can be circulated between the jacket as a heat exchange part, and the tank 4, the addition valve 3 can be cooled efficiently.

  The exhaust gas purifying apparatus 1 according to the second embodiment uses engine cooling water as a coolant for cooling the addition valve 3. That is, according to this exhaust gas purification apparatus 1, as shown in FIG. 2, the water pump 18 that discharges cooling water toward the engine functions as a refrigerant supply means.

In addition, a flow path 21 for guiding the cooling water to the addition valve 3 is branched from a flow path 20 of the cooling water from the water pump 18 toward the engine, and a valve device 22 for changing the opening degree of the flow path 21 is provided. Yes. The valve device 22 is a known solenoid electromagnetic valve similar to the valve device 15 of the first embodiment, and functions as a cooling capacity varying means. That is, the valve device 22 varies the supply amount of the cooling water as the refrigerant of the addition valve 3 by operating the opening degree of the flow path 21 according to a command from the ECU 6.
In the exhaust gas purification apparatus 1 according to the second embodiment, the flow path 12 forming the injection flow path is directly connected to the discharge port of the supply pump 5.

[Modification]
According to the exhaust gas purifying apparatus 1 of the first and second embodiments, the cooling capacity variable means is the valve devices 15 and 22, but automatically operates the opening degree of the flow path 10 and the flow path 21 in response to the temperature. The cooling capacity variable means may be constituted by a thermostat. In this case, since the opening degree of the flow paths 10 and 21 can be operated without being controlled by the ECU 6, the thermostat also has a function of a control means.

  Further, according to the exhaust gas purification apparatus 1 of the first and second embodiments, the opening degree of the flow path 10 or the flow path 21 can be continuously changed according to the energization amount to the solenoid coil of the valve device 15 or the valve device 22. However, when a threshold value (for example, 300 ° C.) is set with respect to the temperature of the exhaust gas, and the detection value from the exhaust gas temperature sensor 16 is equal to or higher than the threshold value, the flow paths 10 and 21 are fully opened. Alternatively, it may be fully closed.

  Further, according to the exhaust gas purification apparatus 1 of the first embodiment, the valve device 15 is disposed in the flow path 10 on the downstream side of the branch point of the flow path 12 and on the upstream side of the jacket. The device 15 may be disposed in the flow path 11.

  In addition, according to the exhaust gas purification apparatus 1 of Example 1, the injection flow path was branched from the flow path 10 as the reducing agent flow path outside the addition valve 3, but the injection flow path was used inside the addition valve 3. The flow path may be branched. That is, the injection flow path may be branched from the reducing agent flow path inside the addition valve 3 such as a jacket.

  Further, according to the exhaust gas purifying apparatus 1 of Examples 1 and 2, the temperature detecting means is the exhaust gas temperature sensor 16 that detects the exhaust gas temperature, but the temperature can be increased by directly attaching the temperature sensor to the addition valve 3. A detecting means may be configured, and a sensor for detecting the operating state of the engine (for example, rotation speed or load) is used as the temperature detecting means, and the temperature of the addition valve 3 is estimated based on a detection value obtained from the sensor. You may make it do.

It is a block diagram of an exhaust gas purification apparatus (Example 1). (Example 2) which is a block diagram of an exhaust gas purification apparatus.

Explanation of symbols

1 Exhaust gas purification device 2 Exhaust pipe 3 Addition valve 4 Tank (supply source)
5 Supply pump (refrigerant supply means)
6 ECU (control means)
10 Channel (reducing agent flow path)
11 Channel (reducing agent flow path)
12 Channel (Injection channel)
15 Valve device (cooling capacity variable means)
16 Exhaust gas temperature sensor (temperature detection means, exhaust gas temperature detection means)
18 Water pump (refrigerant supply means)
22 Valve device (cooling capacity variable means)

Claims (5)

An addition valve that is attached to an exhaust pipe through which exhaust gas from the engine passes and injects a reducing agent stored in a predetermined supply source into the exhaust pipe and is cooled by a refrigerant;
Refrigerant supply means for supplying the refrigerant to the addition valve;
Cooling capacity varying means for varying the amount of the refrigerant supplied to the addition valve;
Temperature detecting means for detecting the temperature of the addition valve;
An exhaust gas purification apparatus comprising control means for controlling the cooling capacity variable means in accordance with a detection value obtained from the temperature detection means. The exhaust gas purification apparatus according to claim 1,
The refrigerant is a reducing agent;
The refrigerant supply means is a supply pump that sucks a reducing agent from the supply source and pumps the reducing agent toward the addition valve,
A reducing agent flow path provided to return the reducing agent pumped by the supply pump as the refrigerant toward the addition valve and to return the reducing agent that has cooled the addition valve to the supply source;
The exhaust gas purifying apparatus according to claim 1, wherein the cooling capacity variable means is a valve device that is disposed at any position of the reducing agent flow passage and varies a flow rate of the reducing agent in the reducing agent flow passage. The exhaust gas purification apparatus according to claim 2,
An exhaust gas purification apparatus comprising an injection flow path that branches from the reducing agent flow passage and into which the reducing agent injected into the exhaust pipe flows. In the exhaust gas purification apparatus according to any one of claims 1 to 3,
The exhaust gas purification apparatus according to claim 1, wherein the temperature detection means is exhaust gas temperature detection means for detecting a temperature of exhaust gas passing through the exhaust pipe. The exhaust gas purification apparatus according to claim 1,
The refrigerant is cooling water for the engine;
The refrigerant supply means is a water pump that discharges cooling water toward the engine,
The exhaust gas purifying apparatus, wherein the cooling capacity varying means is a valve device that varies the flow rate of cooling water from the water pump toward the addition valve.

Images